1. Field of the Invention
The present invention relates to a technique of performing blur restoration based on object distance information in an image.
2. Description of the Related Art
Japanese Patent Laid-Open No. 2000-156823 discloses an image capture apparatus which can calculate object distances based on signals from focus detection pixels discretely distributed among the pixels of an image sensor. Employing the arrangement disclosed in Japanese Patent Laid-Open No. 2000-156823 makes it possible to acquire an object distance distribution in a captured image.
As a method of generating a blur-restored image by restoring a blurred image, there is available a method using a Wiener filter, a general inverse filter, a projection filter, or the like. Japanese Patent Laid-Open No. 2000-20691 discloses a technique of performing blur restoration by using such a method. Using the technique disclosed in Japanese Patent Laid-Open No. 2000-20691 can obtain a degradation function by physical analysis based on image capture conditions and the like or estimation based on an output from a measuring device in an image capture apparatus and restore a blurred image by an image restoration algorithm called deconvolution.
In general, at which object distance focus is to be achieved is decided by a focus state at the time of image capture. For this reason, it is not possible to change the object distance at which focus is achieved after image capture. It is however possible to change the object distance at which focus is to be achieved after image capture by acquiring an object distance distribution in a captured image using the technique disclosed in Japanese Patent Laid-Open No. 2000-156823 and performing blur restoration using the blur restoration technique disclosed in Japanese Patent Laid-Open No. 2000-20691.
However, applying the techniques disclosed in Japanese Patent Laid-Open Nos. 2000-156823 and 2000-20691 to an image processing apparatus will greatly increase the size of resources, require expensive hardware, and take much time for blur restoration processing. This is because, although the range of object distances that allow blur restoration is set by a blur restoration filter corresponding to object distances, blur restoration in the entire range requires an enormous amount of processing contents. In addition, simplifying a blur restoration filter for the simplification of blur restoration processing contents will increase the degree of degradation in the quality of an image after blur restoration.
On the other hand, when an operator captures an image of an object upon rough focus adjustment, it is not necessary to perform blur restoration for the entire range of object distances that allow blur restoration. In this case, finely correcting the focus position relative to a captured image makes it possible to implement restoration intended by the operator. When the operator displays an enlarged captured image, it suffices to perform blur restoration only near the position at which the object displayed within the display range is in focus.